1. Field of the Invention
The present invention relates to a method of producing an ink jet head valve, a method of producing an ink jet head and an ink jet head produced by the method.
2. Related Background Art
An ink jet recording process, the so-called bubble jet recording process, in which a state change including a rapid volume change of ink (i.e., generation of bubbles) is caused to be generated by imparting energy such as heat or the like to the ink, the ink is discharged from a discharge port by an active force due to this state change and the discharged ink is adhered to a medium to be recorded to perform an image formation, has been well known. In the recording device using this bubble jet recording process, as disclosed in publications of the specification of U.S. Pat. No. 4,723,129 and the like, there are generally provided a discharge port for discharging ink, an ink flow path communicated with this discharge port and an electrothermal converting member used as an energy generating means for discharging ink provided in the ink flow path.
According to such recording process, a high quality level image can be recorded at high speed and low noise and a discharge port for discharging ink can be provided at high density in a head in this recording process. Therefore, the recording process has a number of advantages, that including a high resolution recording image and such a color image could easily be obtained in a compact device. Thus, this bubble jet recording process has recently been used in various office equipment such as a printer, copy machine, facsimile and the like. Further, the recording process is used even in an industrial system such as a printing equipment etc.
With the increased use of the bubble jet technology in products in many fields, the following various demands have recently increased.
For example, an answer the demand for improvement of energy efficiency includes optimization of a heating element in which the thickness of a protective film is controlled. This technology has an advantage in that the transmission efficiency of generated heat to liquid is enhanced.
Further, to obtain a high definition image, there is provided a driving condition for imparting a liquid discharging method in which an improved ink discharge based on a stable bubble generation can be performed. Furthermore, to obtain a liquid discharge head having a high refilling speed of a discharged liquid to a liquid flow path from the viewpoint of high speed recording, there is also provided a liquid discharge head having improved shapes of the liquid flow path.
A flow path structure and a head producing method disclosed in Japanese Patent Laid-open Application No. 63-199972, relating to the shapes of the flow path, are inventions directed to a back wave (pressure in a direction opposite to that toward a discharge port, that is, pressure toward a liquid chamber) which is generated with the generation of bubbles. This back wave is known as a loss energy since it is not an energy toward the discharge direction.
A head disclosed in the Japanese Patent Laid-open Application No. 63-199972, has an ink jet head valve which is spaced from a bubbling area of bubbles formed by the heating element and is positioned at the side opposite to the discharge port with respect to the heating element. This valve has an initial position in a manner that it is adhered to the ceiling of the flow path by a head producing method using a plate material, and is hung down in the flow path with the generation of bubbles. This application discloses an invention in which energy loss is controlled by controlling a part of the above-mentioned back wave with a valve.
Further, to realize improvements of liquid discharge properties including control of the back wave, and of liquid supply properties, Japanese Patent Laid-open Application No. 9-201966 discloses a constitution in which a movable member is provided facing a bubble generation area which generates bubbles, and the growth of bubbles is controlled by using displacement of the movable member, generated by pressure at the time of bubble generation.
FIG. 4 shows a partially broken perspective view of one embodiment of a liquid discharging head provided with such ink jet head valve.
In the liquid discharging head in FIG. 4, a heating element 2 which allows heat energy to act on liquid is provided on an element substrate 1 as a discharge energy generating element for discharging liquid. Liquid flow paths 7 are provided on this element substrate 1 corresponding to the heating element 2. The liquid flow paths 7 are communicated with a discharge port 5, and are also communicated with a common liquid chamber 13 for supplying liquid to the plurality of liquid flow paths 7, thereby receiving an amount of liquid corresponding to the liquid discharged from a discharge port, from this common liquid chamber 13.
On the element substrate 1 of liquid flow paths 7 is provided an ink jet head valve in which a 1 .mu.m thick plate-shaped movable member 6 having a flat surface portion, which is composed of an elastic material, such as a thin film resin, metal or the like, is provided like a cantilever beam.
In FIG. 4, when the heating element 2 is heated, heat acts on liquid in a bubble generation region between the movable member 6 and heating element, thereby generating bubbles based on the film boiling phenomena. The pressure and bubbles based on the generation of bubbles act on the movable member 6 and cause the member 6 to be displaced so that the member is largely opened on a liquid discharge side using a fulcrum 6a as the center of rotation, whereby the pressure generated by generation of bubbles and the bubbles themselves can be led to the downstream side where the discharge port 5 is provided.
To produce the above-mentioned ink jet head valve, a valve material produced by an electroforming process or the like was used to laminate the material on a substrate.
When the valve material is laminated on the substrate, it is necessary to provide a space of about 1 to 20 .mu.m between the movable member and heating element so as to sufficiently obtain effects of the movable member. Further, to laminate the valve material produced by the electroforming process or the like so that a space can be formed in the movable portions, it is necessary to form a pedestal portion on the substrate so that a valve is previously fixed onto the substrate.
Further, to form the pedestal portion having for example 5 .mu.m, which is merely the height of the space, and to prevent the pedestal portion from being corroded with ink, it is necessary to form the portion by an Au plating process or the like. To perform the Au plating, sputtering of Au and patterning thereof by the photolithography technology are needed.
Further, it is necessary to provide an electroformed valve on a surface of the Au pedestal after the Au plating, make positioning of the valve and fix the valve by a stud bump process or the like. However, it is difficult to position the valve with high precision.
Therefore, not only the thickness control of the valve and positioning of the valve were difficult, but also the production steps were extremely complicated.
Accordingly, the objects of the present invention are to solve the above-mentioned problems and provide a method of producing an improved ink jet head valve, a method of producing an ink jet head, and an ink jet head produced by the method.